GE-Enforce: re-mount W: before status write + null guards

Root cause of fleet not reporting: long-running entries (UDC's
WaitTimeoutSec=120) keep the dispatcher CPU-busy with no SMB traffic
to W:. SMB server times out the idle session. W: stays as a "mapped"
drive letter on the client but Path operations against it fail with
weird errors (e.g. "Cannot bind argument to parameter 'Path' because
it is null" via downstream Join-Path / Test-Path null cascades).

Fix:
- Re-attach W: at the top of the status write-back block (cheap; if
  still alive net use returns 'already mapped'; if dead, freshly
  remounts).
- Null-guard $hostname (fall back to 'UNKNOWN') and explicitly throw
  if $driveLetter is unset (catch surfaces a clear error in log).
- Pair with UDC manifest WaitTimeoutSec reduction 120 -> 60 on the v2
  share to limit how long the SMB stays idle in the first place.

Surfaced via blah*.txt log captures from 3 deployed bays (3105, 3115,
3116, 3118 era) - all showed "Status write-back failed: Cannot bind
argument to parameter 'Path' because it is null" while everything
upstream (manifest entries) ran clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

playbook/shopfloor-setup/common/GE-Enforce.ps1

@@ -236,10 +236,19 @@ try {
     # continues if the share path is not writable.
     # ------------------------------------------------------------------
     try {
+        # Re-mount W: before status write-back. Long-running entries (UDC
+        # WaitTimeoutSec=120) can let the SMB session time out idle, leaving
+        # W: as a dead drive letter that fails downstream Path operations
+        # with confusing "argument is null" errors. Cheap to re-attach.
+        & net use $driveLetter /delete /y 2>$null | Out-Null
+        & net use $driveLetter $shopfloorShareRoot /user:$($cred.Username) $($cred.Password) /persistent:no 2>&1 | Out-Null
+
         # Live NetBIOS name from kernel - not $env:COMPUTERNAME, which is
         # cached in the process env block and goes stale after a post-image
         # rename on Intune-managed PCs.
         $hostname   = [System.Environment]::MachineName
+        if (-not $hostname) { $hostname = 'UNKNOWN' }
+        if (-not $driveLetter) { throw 'driveLetter unset before status write-back' }
         $statusDir  = Join-Path (Join-Path $driveLetter '_outputs') (Join-Path 'logs' $hostname)
         if (-not (Test-Path $statusDir)) {
             New-Item -Path $statusDir -ItemType Directory -Force -ErrorAction Stop | Out-Null